1. Field of the Invention
The present invention refers to a screw nut comprising a screw nut body, a central inner thread provided in said screw nut body and a radially extending slit provided in said screw nut body, the width of said radially extending slit essentially corresponding to the diameter of said central inner thread, and being adapted to enable a threaded bolt or a threaded stud to be radially inserted into said screw nut body.
Such a screw nut can be engaged with a threaded bolt or a threaded stud at any arbitrary position of the thread thereof, whereby the need is removed to laboriously turn the nut onto a long bolt or stud until a desired position is reached.
Furthermore, the invention refers to a method of manufacturing a screw nut comprising a screw nut body, a central inner thread provided in said screw nut body a radially extending slit provided in said screw nut body and having a first and a second side wall, the width of said radially extending slit essentially corresponding to the diameter of said central inner thread, and being adapted to enable a threaded bolt or a threaded stud to be radially inserted into said screw nut body, whereby said central inner thread comprises a plurality of thread turns provided with axially extending recesses directed towards the end surface of the screw nut which is under load when said screw nut body is tightened on said threaded bolt and threaded stud, respectively.
2. Prior Art
According to the publication PCT-WO 86-01266, a two-piece screw nut is disclosed which put on a threaded stud at any arbitrary position of said threaded stud. For this purpose, a screw nut is described which comprises two segment or half moon shaped parts which are put around the threaded stud and snapingly lock to each other such that the screw nut so formed can be tightened on the threaded stud. The disadvantage of this screw nut is that it is time-consuming and expensive to manufacture, troublesome to handle and that it can be loosened only by means of a special tool.
A three-piece screw nut which can be put on a threaded bolt at any arbitrary position thereof without the need to screw it on the stud from the end is disclosed in the publication PCT-WO 87-07928. It comprises two parts which together really form the screw nut, i.e. a screw nut which is divided into two halves by a plane running through the central axis plane of it. The two halves are provided with an outer thread adapted to receive a locking nut. The two halves of the real nut are put around the threaded stud in the desired position, then the locking nut is put over the end of the threaded stud and displaced towards the two halves of the real nut, and finally the locking nut is screwed onto the outer thread of the two halves of the real screw nut. Also in this case, a complicated and, thus, expensive manufacture is required. A further disadvantage is that the locking nut must be put over the end of the threaded stud; consequently, this design cannot be used of the end of the threaded stud is not freely exposed or easily accessible.
According to U.S. Pat. No. 1,375,781, a one-piece screw nut is disclosed which can be put on a threaded bolt at any arbitrary position thereof. For this purpose, the screw nut comprises a radially running slit opening into a centrally arranged bore. The central bore is provided with thread turns extending over not more than half of its circumference. It must be admitted that this screw nut is of simple design and the handling thereof is easier than the one of the screw nuts described hereinbefore. However, the disadvantage is that this screw nut has the tendency, upon tightening, to move radially away from the threaded bolt with the consequence that only a very small part of the thread of its central bore engages the thread of the bolt. Even if this screw nut is made of heavy duty steel material, it is suited only for low torques.
Finally, the German Utility Model Nr. 71 46 313 discloses a screw nut which can be put onto the thread of a threaded bolt or stud at any arbitrary location as well. With this design, the tendency that the screw nut radially displaces from the threaded stud or bolt upon tightening, however, is less because the slit provided in the screw nut has less width than the diameter of the threaded bolt or stud. On the other hand, in order to enable the screw nut to be placed on the thread of the bolt or stud, the screw nut body must be made of elastically resilient material. This fact, however, limits the maximally applicable torque to a comparatively low value upon tightening the screw nut, because the screw nut cannot be manufactured of a heavy duty steel material as, in that case, the forces required to elastically deform the screw nut upon placing it onto the threaded stud or bolt would be much too high.